Composite materials are used in a wide variety of applications. In aircraft construction, composites are used in increasing quantities to form the fuselage, wings, tail section, and other components. During the forming of composite structures, composite plies may be laid up on a tool having the shape of the final composite part. Heat and/or pressure may be applied to the composite plies to cure or solidify resin material in the composite plies. Compactive pressure may be applied to the composite layup by covering the layup with a vacuum bag, sealing the vacuum bag to the tool, and drawing a vacuum on the vacuum bag. Additional pressure may be applied by placing the bagged layup into an autoclave. The compactive pressure of the vacuum bag may force the composite plies against the tool surfaces during cure such that the final composite part assumes the shape of the tool. The compactive pressure may also consolidate the composite plies and assist in removing excess resin which may increase the fiber-volume fraction and thereby increase the specific strength of the final composite part. In addition, the application of compactive pressure may assist in removing volatiles (e.g., gasses) and/or moisture generated during the heating and curing of the resin and may also assist in preventing voids in the final composite part.
For tool surfaces that include inside corners or female radii, the vacuum bagging process may require the forming of pleats of excess material in the vacuum bag at locations where the vacuum bag compresses the inside corners of the composite layup. Pleats may be hand-formed by folding the vacuum bag material over onto itself and sealing together the overlapped material at the edges of the vacuum bag. The formation of pleats allows for localized slippage of the vacuum bag in the region of the inside corner as the composite layup shrinks in thickness under the force of the compactive pressure. Pleats are typically necessary to prevent bridging of the vacuum bag and composite plies in the region of the inside corners. Such bridging may result in a reduction in consolidation of the composite plies, and may result in the inside corners having excess resin and an increased risk of voids or porosity in the final composite part.
Unfortunately, the forming of pleats in a vacuum bag is a time-consuming and labor-intensive process requiring a significant amount of touch labor. In this regard, each pleat must be hand-formed in a meticulous manner and must be adjusted such that the pleat is aligned with the length of the inside corner. Each pleat may also represent a possible leak path into the vacuum bag which may compromise the integrity and robustness of the vacuum bagging process.
As can be seen, there exists a need in the art for a system and method for vacuum bagging a composite layup in a manner that allows for the application of compactive pressure in inside corners of a composite layup and which can be implemented in a reduced amount of time and with a reduced amount of touch labor and which has a high degree of robustness.